In this paper we present a multi-pass rendering approach for approximating the effects of multiple refractions and specular reflections in transparent or semitransparent materials. These optical effects are typically found in natural materials like ice but also in glass artworks. The rendering technique proposed in this paper is intended to perform at real-time frame rates and aim at achieving naturally looking effects rather than simulating physically correct interaction between light and matter. Part of our method is an improved image space technique for clipping a geometry using the Boolean difference of two geometries in order to create internal surfaces of reflection inside transparent objects. It employs a number of generic cracks surface geometries which are clipped against the geometry to be rendered. Reflection and refraction effects on the ice are implemented by using environment mapping. Two-sided refraction is accomplished by combining the normal vectors of the front and back side of the ice object. Our method renders icy objects with convincing visual appearance in real-time on state-of-the-art graphics hardware.